Oscillator modulator



May 25 1948- E. J. coxEY OSGILLATOR MODULATOR Filed April 4, 1944 0 0T www hmm INVENTOR. Edu/md j Z2/ey Patented May 25, 1948 c 2,441,955 AT .v voscntmi'roit MoDULAToa Edward '.I. Coxey, Little Falls, N. assigner to. Federal Telephone and Radio Corporation, New York, N. Y., a corporation of Delaware Application april 4, 1944, serial No. 529,449

This invention relates to new and useful improvements in electric oscillatorsrand more par- 8 Claims. (Cl. 17g-171.5).

ticularly in oscillator-modulator circuits producf ing oscillations and applying such oscillations to modulate a high voltage supply such as is used 4in radio transmitters. Y

One of the objects of this invention is to provide a modulator-oscillator with a minimum of parts.

.Another object of the invention is to reduce circuit losses to a minimum and to obtain 100% modulation by simple means.

A further object of the invention is to provide a fully modulated D. C. power supply for an intermediate or the final stage, particularly for the tank circuit of a. transmitter as used in ship communications or wherever a modulator using a minimum of .components is needed.

A specific object of the invention is to provid asingle inductance element, serving both as oscillator and modulator element.Y

Still another object of the invention is an audio-oscillator modulating -a transmitter by means of 'acombined oscillator and modulator transformer. f Y

An additional object of the invention isan audio-oscillator, of the magnetic` or capacitive feedbackv type, comprising a transformer serving simultaneously as an oscillation inductance and as a modulation transformer feeding the plate circuit of an intermediate or the final stage of y a radio transmitter.

Further objects and advantages of the invention will be apparent from the following description applied to the drawing.

A preferred embodiment of the invention is diagrammatically shown in the drawing, Fig. 1 illustrating as much of an audio frequency oscillator of the Hartley type as is necessary for an understanding of the principles of the invention. Fig. 2 is a diagram of a modified circuit. Iny Fig. l, I is an audio-oscillator tube in circuit with a transformer 2. Winding 3 of transformer 2 connects, at one terminaLto the grid of tube I and, at its second terminal, over grid leak resistor 4 and grid blockingcondenser 5 to ground. Second winding 6 of transformer 2 connects to the plate of tube I. The oscillator thus formed represents a modified Hartley or magnetic feedback circuit. 'I'uning condenser I2 may be used in parallel with transformer winding 6 or with any other part of transformer 2, as required.` Transformer winding 6 is connected to the high voltage B+ and also grounded over Joy-pass condenser 1. B+ supplies plate *UNITED f STATES PATENT. cfm

current and feeds a tank circuit ll in a preliminary or the nal stage of -a radio frequency amplifier. The modulated voltage is taken offv at 8 from the oscillator-modulator circuit. 9 is a radio frequency by-pass condenser.V

In this diagram the singlecomponent 2 is shown to operate as a modulation transformer as well as an inductance ofthe oscillator circuit.

Instead yof a transformer such as shown in Fig. 1, an autotransformer yor any other inductive coupling -means may beused as required to achieve the object of the invention. Y

The circuit shown in Fig. 2 employs a modified Hartley oscillator, 'the inductive portion of which, an auto-transformerrlB, Ais extended` at |44 to match the load impedance presented by the modulated radior frequency amplifierV I5. This may be used to'obtain a 100% lmodulation supply of D. C. fora preliminary orfthe nal stage ofaradio transmitter.

The invention is not restricted to modulating the D. C. supply of a finalv amplifier stage. It may be found desirable toV plate modulate a low power stage and amplify the modulated routput of the low power stage by ymeans of higher power linear amplifiers. Y

The invention is not limited to the type of oscillator shown. Many types of oscillators, such as capacity feedback oscillation circuits. may be adapted to obtain oscillation-modulation in .accordance withl the invention, without exceeding the scopethereof. l .Y Y

The invention is-not limited to the method and type of modulation in which. the"v modulating `signal is applied in the plate circuit of aradio frequency power amplier.

-There is no limitation tothe frequency or frequency range which may be used in accordance with this invention as 'modulator frequencylor carrier. frequency..However, the invention mayfoffer particulary advantages4 for the modulation of a high voltage D. C. powerfsupply used in marine transmitters.

What is claimed is:l

Y 1. An -oscillatorfmodulator system` for a Aradio transmitter having a-plurality ofstages, comprising an oscillator tube for producing audio frequencies, said tube having a grid circuit comprising one winding of a transformer, a tank circuit comprising a second winding of said transformer, a source of positive D. C. power supply applied to one end of said second winding, capacitance tuning means in parallel to said second winding, a tank circuit of a high frequency containing an nductance portion extending Vloepedance of said coil approximately matching,

at an audio frequency, the load impedance presented by the output circuit of saidhigh frequency amplier, means for `adjustingthe im-4 pedance of the coil andan audoIosc'iilator/f fu.)lsalidfwindingendl-and said point, whereby said ulate to cut off the direct current flowing-through f coupled across a portion of 'said coilfto mod the coil to said high frequency stage'.

3. In a radio transmitter, a high frequency,V

impedance of `said coi'lapproximately 'match-1 ing, at an audio' frequency,jthe output impedance of said high frequency stage, a tuning capacitor and means including; a? Space discharge device connectedacross spaced`points on said coil f or generating andisuperposing a pulsating voltager at the said audio frequency on the' dir ect current ovving to' s aidzhigh frequency stage, the magnitude of said` current beingsufficient-V at alternateY peak values to` substantially-:stop the flow. of .currentfrornj said source to said; transmitten.V Y Y 4. In la device formodulating `tlfiefoutput of- `a carrier frequencysystem, a sourceof anode current for VsaidY system, any inductive Winding having a plurality of ccnriectionsl thereto, one --of said connections beingvadjustablega space discharge device connected asan oscillator utilizing andanother. portion 'extending beyond said-r'stnamed portion and `including Vsaid-L adjustable' connection. Y

5. -In a device;formodulating-theoutputof a Vcarrier frequency systemy'asource of-anode current Vfor jsaidgsystem; an; inchici-,ive` winding havingja pluralityof connections;thereto,-one of saidu connections being adjustable; i -a space dis- ;charge device connectedas anos'cill'ator-modulating saidoutput and-utilizing a portion ofsaid WindingY as any inductive element-,iV and other connections from saidsourcetosaid systemfincluding a part of saidjportionof' saidwindingutilized as an inductive elementandanother portion extending beyond saidirst-named-portion* and including said adjustable connection;l said adjustable connection .beingjfurther connectedto d etermine in` part by itsv position the degreei'of modulation vproduced in said system by` said oscillator. Y Y ,Y v

6. In adevice for modulating the output'o'f a system containingl oneV or more space discharge devices, at leastone ofjsaid devices operatingas Y Y 4 an oscillator, a source of anode voltage, a connection leading to the anode circuit of one or more space ydischarge devices withiin said system, an inductive winding having an adjustable portion thereofjoining said source and said connection, a space discharge device external to said system having, a, cathode, anode A and a controlfgrid, azsecond connection fromsaid cathode to ground', a third connection through a blocking condenser from said control grid to the end of Vsaid windingV not included in said first-named 'portiong afourth connection from said anode to apoint insaid,r stvnamed portion of said Winding, and'avariab-le- Vcapacitor connected across external space'discharge device will operate as anzoscillatrfproducing a degree of modulation `of saidfsystem determined in part by the particular setting of said adjustable Winding p0rtion, said variable capacitor serving in part to determine the! frequency; ofi saidi oscillations.-

'1; In a-jdevipe forfnroduianng the output om systemcontaining-an-oscillator;ia source of'a'ode voltage, a connection. tottheanodecircuit 'ofsaid system, al winding .conne'ctedl' insa'idfanode circuit a plurality of taps on said'winding, afspace discharge device having.: a cathode, anf anode and` a' contro-lgrid,V a Vconnection' frornsaid cath'` ode to ground,- a second connection fromi'said' control grid throughf: ai blcking condenser.l to one end of said Winding', :a third: connectionfrom the one of said taps nearestfsaidoscillator anode connection to saidfanoole; avariablefcapacitor connected across said last-namedftapandL said end off said- Winding., .a fourth; connection from "said source'rto a second tapinter-mediate said Winding end'fd and saidiirst-nameda-tap, and? a fifth connectionifrm. saidi system anoc'le i circuit connection:A to said- Winding, Vsaid`conne`ction 'heing adjustablyl connectabletothose portionsof said Winding at, in proximityto,l andi extendingV 8. l In con'lbinationz*ani` amplier' and means for modulatingV said; amplifierA ccunprisin'g` anoscillator and a transformena portion oftfsaid'transformer coupledto` fsaid oscillator andforming the: tank circuitthereof, a direct', voltage Asupply sourcecoupled Vtofsaidl` one portion, and? means for couplingsalid; amplifier to" another portionv of saidtransfor-mer l for modulation thereby.`

` f f v EDWAnnzJrCQXEY;

Y Y REFERENGES, r-rED-w- The following references aref of l1feco'1-ci-inthe 

